16' alum springbok with 60hp Evinrude

arnott1t

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Jul 19, 2012
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Hi all, Trying to trouble shoot some poor performance on my new to me boat. The boat is an 82 Springbok Rocket 3 16' aluminim. On the back is an 82 60hp Evinrude twin cylinder. It currently has an 11.75x17" prop. I'm having a hard time getting on plane and also have a low top speed. I don't have a tach but it seem like the motor is bogging some. I have checked the carbs and the butterflies are opening completely. On my GPS tonight we hit a top speed of 27mph with about 450lbs of mammal in the boat and an almost empty tank of fuel. I tried a few different pin settings on the for trim. On the lowest hole it seemed to be pushing the nose down to much and we were plowing water. One notch up was pretty good until a hard turn. Then the prop would spin out and revs would increase dramatically while the boat slowed way down. Another hole higher had the prop slipping on the straights even.

The motor has a whale tail on it install on the cavitation plate. When lowered the motors site with the cavitation plate even with the bottom of the keel.

On a previous day with 4 people and more weight it didn't have a chance to get on plane. Even now its slow to plane out. I'm hoping to use it to pull a tuber and maybe a skier if possible... I don't really need to go fast and would rather get on plane and be able to pull. Currently the boat does neither.

The prop on it now is pretty dinged up and the blades seem cupped or bent up some. I'm sure this could be contributing to my issues. Tomorrow I'm off to look for a tach and a new prop. I'm thinking on dropping pitch to a 15 or 13.

Any comments or advice would be fantastic!!!

Thanks in advance,
Tyler
 

BonairII

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Jun 7, 2011
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2,727
Re: 16' alum springbok with 60hp Evinrude

If it's bogging...your timing may not be advancing smoothly. Check to make sure timer base is rotating properly when throttling up.

Your motor should plane easily with that motor. Are you sure that your flotation foam isn't waterlogged?

Get your motor running correctly BEFORE buying a prop. Dropping pitch to get more rpm is a band-aid not a cure....and probably won't get you up on plane anyway.

At 27mph you definitely should be up on plane. Distributing weight may help some.
 

arnott1t

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Jul 19, 2012
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Re: 16' alum springbok with 60hp Evinrude

If it's bogging...your timing may not be advancing smoothly. Check to make sure timer base is rotating properly when throttling up.

Your motor should plane easily with that motor. Are you sure that your flotation foam isn't waterlogged?

Get your motor running correctly BEFORE buying a prop. Dropping pitch to get more rpm is a band-aid not a cure....and probably won't get you up on plane anyway.

At 27mph you definitely should be up on plane. Distributing weight may help some.


Yes it was certainly on plane then. I can see that the lower timing moving. Is there a way to ensure its moving enough? What about the carb sync? When the prop did slip the motor was able to rev out. but that may be due to just so little load. The foam was wet on the bottom towards the side. I'll look into that as well. What prop would you recommend? What speeds should be within reach?
 

BonairII

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Jun 7, 2011
Messages
2,727
Re: 16' alum springbok with 60hp Evinrude

Yes it was certainly on plane then. I can see that the lower timing moving. Is there a way to ensure its moving enough? What about the carb sync? When the prop did slip the motor was able to rev out. but that may be due to just so little load. The foam was wet on the bottom towards the side. I'll look into that as well. What prop would you recommend? What speeds should be within reach?

If you have the service manual, do the "link-n-sync" to make sure your timing is advancing correctly as carb butterflies open. Yup, the motor will rev high with no load on it.

I can't recommend a prop until you get your motor running correctly, know your motors optimum operating range(should be stamped on the transom bracket), and you know what rpm you are running at WOT.

I run a 17p on my 75hp(see my signature). Since you run heavy(4 people etc) I'm guessing that you're going to need to drop pitch by a couple(or a few) inches. Don't buy another prop, though...until you get your motor/boat running correctly.

Probably wouldn't be a bad idea to get your boat/motor weighed(feed store, local dump, etc) to see if you're waterlogged.
 

steelespike

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Joined
Apr 26, 2002
Messages
19,069
Re: 16' alum springbok with 60hp Evinrude

If the whale tail is in the e water at speed it will eat up some top speed.
If it won't plane quickly with a moderate load there are major problems some where.
While your prop is at the top of the list with only one higher listed here at iboats no changes yet till we eliminate other things listed.
Any physical changes do one at a time and test. Try it without the whale tail ,see if it gives you more speed.Check for water in the foam under the floor.Sometimes if you raise the bow on the trailer you may have a constant trickle of water running to the stern.
 

arnott1t

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Jul 19, 2012
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Re: 16' alum springbok with 60hp Evinrude

Well changed a few different things. I was at the lake this weekend and started ripping floor boards and foam. Most of the floatation foam was saturated and weighed a ton. Coupled with wet carpets and wet plywood I bet I removed 2-300lbs of material. I also purchased a 12.25x15" prop and hit the lake. With just me the boat jumps on plane and can hit 30mpg. With 600lbs or more in it still planes out nicely and can cruise at 27mph. Pullling a tube I could get 25-26 with a big guy in it. I still have some more foam to pull uot as I left the seats in the boat and didn't bother lifting them out. That will come next. Then I need to seal this damn thing. I applied some "Right Stuff" RTV silicone to stope the worst of the leaks but am looking now for some gluvit. I did buy some sikaflex 292...will it work as a sealant though it says its an adhesive?

Thanks for all the help.

Once i get a tach and clean up the dings in the old 17 pitch prop I'll take it for a test too..
 

steelespike

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Apr 26, 2002
Messages
19,069
Re: 16' alum springbok with 60hp Evinrude

Very roughly figured at 30 mph your probably turning about 5400.
 

steelespike

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Apr 26, 2002
Messages
19,069
Re: 16' alum springbok with 60hp Evinrude

As long as your gutting it you could check for any weak spots including the transom.
Also anything not specifically for the bottom may just scrub off from the water action.
 
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